Transparent window films are adhered to glass window surfaces so as to reduce the amount of near infra-red, ultra-violet and/or visible radiation entering interior building space. Films are also provided so as to maintain heat in the interior space--that is, to reduce heat radiation loss through the window. The window films thus assist to minimize loads on the heating, ventilating and air conditioning (HVAC) system which services the building. Lower HVAC loads thereby translate into lower costs of heating or cooling the interior building space.
Such "solar films" can have a variety of film structures. For example, one common type of solar film is a laminate structure having a base layer (e.g., a transparent polyester sheet, such as polyethylene terephthalate sheet) having a relatively thin, transparent solar reflective metallized deposit thereon. A protective layer (e.g., polyethylene terephthalate) may then be applied over the solar reflective layer. See, for example, U.S. Pat. No. 4,634,637, the entire content of which is expressly incorporated hereinto by reference.
Solar films are typically adhered physically to a surface of a glass window using a suitable transparent adhesive, such as those disclosed in U.S. Pat. Nos. 4,429,005 and 4,408,021, the entire content of each patent being incorporated expressly hereinto by reference. In general, the window films are cut to substantially cover the entire window glass area, except for a small border region between the edges of the film and the window frame (typically on the order of between about 1/16 inch to about 1/8 inch). In order to protect the solar film from the degradative effects of window cleaners and other ambient atmospheric conditions (e.g., moisture and salt), it may be necessary to seal the edges of the window film with a suitable sealant. In this way, the sealant substantially minimizes (and most preferably prevents) degradative chemical attack on the individual layers of the solar film so that it retains its appearance over its useful life.
Broadly, therefore, the present invention is directed to transparent edge sealed window films which substantially minimize (if not eliminate entirely) degradative effects on the window film, particularly solar-reflecting metals and/or oxides associated with multilayer window films, caused by ambient conditions (e.g., commercial window cleaners, salt and the like).
In particular embodiments, the edges of window films are sealed by a liquid solvated polymeric material which, upon curing, provides a solid transparent seal which significantly minimize the degradative effects of the ambient environment. Most preferably, the window film whose edges are sealed will include a transparent thermoplastic (e.g., a polyester) film layer and a solar-reflecting metal and/or oxide applied onto a surface of the film layer. The sealant for such a preferred window film will most preferably be a polyester-type sealant which has silane end-group functionality and substantially no free isocyanate groups. The silane end groups of the preferred sealant chemically attach to both the glass substrate on which the window film is adhered in addition to the oxides in the film at the cut edges. Furthermore, the polyester resin in the sealant will bond with the thermoplastic forming the film layer. As a result, an impermeable edge seal is formed which withstands attacks on the film components by conventional window cleaning chemicals as well as significantly minimizing, if not preventing entirely, corrosion of the metallized deposit on the film layer (e.g., when subjected to ASTM B-117 Salt-Fog Exposure).
Further aspects and advantages of this invention will become more clear after careful consideration is given to the following detailed description of the preferred exemplary embodiments thereof.